1. Field of the Disclosure
The present disclosure relates to a method of fabricating a nitride-based semiconductor laser diode, and more particularly, to a method of manufacturing a nitride-based semiconductor laser diode that can minimize optical absorption on a cavity mirror plane and improve the surface roughness of the cavity mirror plane.
2. Description of the Related Art
In an edge-emitting semiconductor laser diode, when laser light emerges from an exit surface, the semiconductor crystalline structure on the exit surface is distorted due to high photon density and Joule heating, thereby increasing optical absorption and laser threshold current. An increased laser threshold current may degrade the thermal characteristics of the laser diode, thus increasing the optical absorption on an exit surface. The degradation in optical characteristics occurs exponentially and becomes a major factor leading to an abrupt shortening of the life span of a semiconductor laser diode. This is called a ‘catastrophic optical damage’ (COD).
A quality factor (Q) indicating laser cavity efficiency is one of primary factors influencing the characteristics of a semiconductor laser diode. The roughness of a cavity facet is one of the most important factors in determining the quality factor Q. As the roughness of the cavity facet is closer to zero, the quality factor Q increases, thus improving the laser characteristics. A cavity mirror plane is formed using notch and cleaving during the manufacturing of a nitride-based semiconductor laser. As widely known in the art, it is difficult to form a cavity mirror plane having a roughness close to that of an atomically single plane using this technique.
Thus, there is an urgent need to develop a process of manufacturing a semiconductor laser diode that can minimize optical absorption on a cavity mirror plane by forming a cavity mirror plane with an improved roughness close to that of an atomically single plane.